ADP1710AUJZ-1.5-R7 datasheet(11/16 Pages) AD

11 / 16 page

ADP1710/ADP1711

Rev. 0 | Page 11 of 16

Current and thermal limit protections are intended to protect

the device against accidental overload conditions. For reliable

operation, device power dissipation must be externally limited

so junction temperatures do not exceed 125°C.

THERMAL CONSIDERATIONS

To guarantee reliable operation, the junction temperature of the

ADP1710/ADP1711 must not exceed 125°C. To ensure the

junction temperature stays below this maximum value, the user

needs to be aware of the parameters that contribute to junction

temperature changes. These parameters include ambient

temperature, power dissipation in the power device, and thermal

resistances between the junction and ambient air (θJA). The θJA

number is dependent on the package assembly compounds used

and the amount of copper to which the GND pins of the package

are soldered on the PCB. Table 5 shows typical θJA values of the

5lead TSOT package for various PCB copper sizes.

Table 5.

Copper Size (mm2)

θJA (°C/W)

170

152

100

146

300

134

500

131

1 Device soldered to minimum size pin traces.

The junction temperature of the ADP1710/ADP1711 can be

calculated from the following equation:

TJ = TA + (PD × θJA)

(2)

where:

TA is the ambient temperature.

PD is the power dissipation in the die, given by

PD = [(VIN – VOUT) × ILOAD] + (VIN × IGND)

(3)

where:

ILOAD is the load current.

IGND is the ground current.

VIN and VOUT are the input voltage and output voltage,

respectively.

Power dissipation due to ground current is quite small and can

be ignored. Therefore, the junction temperature equation

simplifies to the following:

TJ = TA + {[(VIN – VOUT) × ILOAD] × θJA}

(4)

As shown in Equation 4, for a given ambient temperature, input

to output voltage differential, and continuous load current,

there exists a minimum copper size requirement for the PCB to

ensure the junction temperature does not rise above 125°C. The

following figures show junction temperature calculations for

different ambient temperatures, load currents, VIN to VOUT

differentials, and areas of PCB copper.

140

0.5

5.0

VIN – VOUT (V)

120

100

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1mA

10mA

30mA

80mA

100mA

125mA

150mA

(LOAD CURRENT)

MAX TJ (DO NOT OPERATE ABOVE THIS POINT)

Figure 23. 500 mm2 of PCB Copper, TA = 25°C

140

0.5

5.0

VIN – VOUT (V)

120

100

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1mA

10mA

30mA

80mA

100mA

125mA

150mA

(LOAD CURRENT)

MAX TJ (DO NOT OPERATE ABOVE THIS POINT)

Figure 24. 100 mm2 of PCB Copper, TA = 25°C

140

0.5

5.0

VIN – VOUT (V)

120

100

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1mA

10mA

30mA

80mA

100mA

125mA

150mA

(LOAD CURRENT)

MAX TJ (DO NOT OPERATE ABOVE THIS POINT)

Figure 25. 0 mm2 of PCB Copper, TA = 25°C

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